%I #8 Sep 19 2018 08:49:48

%S 6,116,1620,19764,224532,2440692,25745364,265720500,2697594516,

%T 27033340788,268094978388,2636009007156,25732468879380,

%U 249667710249204,2409688805255892,23151313964420532,221538858133842324

%N Number of defective 3-colorings of an n X 4 0..2 array connected horizontally and antidiagonally with exactly one mistake, and colors introduced in row-major 0..2 order.

%H R. H. Hardin, <a href="/A229582/b229582.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 18*a(n-1) - 81*a(n-2) for n>3.

%F Conjectures from _Colin Barker_, Sep 19 2018: (Start)

%F G.f.: 2*x*(3 + 4*x + 9*x^2) / (1 - 9*x)^2.

%F a(n) = 4 * 9^(n - 2) * (16*n - 3) for n>1.

%F (End)

%e Some solutions for n=3:

%e ..0..1..0..1....0..1..1..2....0..1..0..2....0..1..2..1....0..1..2..0

%e ..0..2..1..2....0..2..0..2....0..1..0..2....0..1..0..1....1..0..1..0

%e ..1..0..1..0....0..2..1..0....1..2..1..2....1..2..0..2....1..2..1..0

%Y Column 4 of A229586.

%K nonn

%O 1,1

%A _R. H. Hardin_, Sep 26 2013